PHP数组未设置字符串

Question

I am trying to unset a group of array keys that have the same prefix. I can't seem to get this to work.

foreach ($array as $key => $value) {
    unset($array['prefix_' . $key]);
    }

How can I get unset to see ['prefix_' . $key] as the actual variable? Thanks

UPDATE: The $array keys will have two keys with the same name. Just one will have the prefix and there are about 5 keys with prefixed keys:

Array {
   [name] => name
   [prefix_name] => other name
}

I don't want to remove [name] just [prefix_name] from the array.

Answer 1

You can't use a foreach because it's only a copy of the collection. You'd need to use a for or grab the keys separately and separate your processing from the array you want to manipulate. Something like:

foreach (array_keys($array) as $keyName){
  if (strncmp($keyName,'prefix_',7) === 0){
    unset($array[$keyName]);
  }
}

You're also already iterating over the collection getting every key. Unless you had:

$array = array(
  'foo' => 1,
  'prefix_foo' => 1
);

(Where every key also has a matching key with "prefix_" in front of it) you'll run in to trouble.

Answer 2

I'm not sure I understand your question, but if you are trying to unset all the keys with a specific prefix, you can iterate through the array and just unset the ones that match the prefix.

Something like:

<?php
foreach ($array as $key => $value) {      // loop through keys
    if (preg_match('/^prefix_/', $key)) { // if the key stars with 'prefix_'
        unset($array[$key]);              // unset it
    }
}

Answer 3

This works:

$array = array(
  'aa' => 'other value aa',
  'prefix_aa' => 'value aa',
  'bb' => 'other value bb',
  'prefix_bb' => 'value bb'
);

$prefix = 'prefix_';
foreach ($array as $key => $value) {
  if (substr($key, 0, strlen($prefix)) == $prefix) {
     unset($array[$key]);
  }
}

If you copy/paste this code at a site like http://writecodeonline.com/php/ , you can see for yourself that it works.

Answer 4

You're looping over the array keys already, so if you've got

$array = (
    'prefix_a' => 'b',
    'prefix_c' => 'd'
     etc...
)

Then $keys will be prefix_a , prefix_c , etc... What you're doing is generating an entirely NEW key, which'd be prefix_prefix_a , prefix_prefix_c , etc...

Unless you're doing something more complicated, you could just replace the whole loop with

$array = array();

Answer 5

I believe this should work:

foreach ($array as $key => $value) {
    unset($array['prefix_' . str_replace('prefix_', '', $key]);
}